Celestial navigation trainer



Dec. 5, 1944.

Filed Dec. 28, 1942 ll Sheets-Sheet l 224 62 a as so FIG. I

EDWIN A. LINK INVENTOR.

ATTORNEY.

Dec. 5, 1944. E. A. LINK CELESTIAL NAVIGATION TRAINER Filed Dec. 28,. 1942 11 Sheets-Sheet 2 EDWIN AILINK BW/f ATTORNEY.

Dec. 5, 1944.

I E. A. LINK CELESTIAL NAVIGATION TRAINER File d Dec. 28, 1942 11 Sheets-Sheet 5 7a 472 so 92 uo 0 h I l I 4 I58 I 402 Ill I28 I l FIG. 3

EDWIN A. LINK INVENTOR.

ATTORNEY.

11 Sheets-Sheet 1944. E. A. LINK CELESTIAL NAVIGATION TRAINER j 7 Filed Dec. 28, 1942 I5 I46 I I48 I50 I27 I F I "h I A 10 7 I2 I 126 I I56 I52 I66 I I II IGI I62 I64 I45 FIG. 4

EDWIN A; LINK INVENTOR.

ATTORNEY rm. 5, 1944. E. A. LINK CELESTIAL NAVIGATION TRAINER Filed Dec. 28, 1942 ll Sheets-Sheet 5,

ii L.

EDWIN A. LINK INVENTOR.

ATTORNEY.

Dec. 5, 1944. LlNK 2,364,539

CELESTIAL NAVIGATION TRAINER Filed Dec. 28, 1942 ll Sheets-Sheet 6 LONGUDE m1: ILL m0 W 2 OFFON msc. off ON F IG. 6

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Haw/rm Y ATTORNEY.

Dec. 5, 1944. LINK 2,364,539

CELESTIAL NAVIGATION TRAINER Filed Dec. 28, 1942 ll Sheets-Sheet 7 EDWIN A. LINK INVENTOR.

ATTORNEY.

E. A. LINK Filed Dec. 28, 1942 CELESTIAL NAVIGAT ION TRAINER ll Sheets-Sheet 8 EDWIN A.,L|NK' INVENTOR.

BYW/ Wm- ATTORNEY.

Dec. 5, 1944. E. A. LINK GELESTIAL NAVIGATION TRAINER,

Filed Dec. 28, 1942 ll Sheets-Sheet 9 000000 0000. 000 2 0 s 0 O 0. 0 0 0 0 0 u u u 0 0 0 0000000. 00000000100000000 .000 0000000-x0000000000 .000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 0 0 0 4 4 0 4 .0 0 000000000 0 0 0 00 000 00 000000000 .0 0. 0 0 0 0 0 0 .0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 00000 00/ 00000000 0 0 0 Z 00. 90 00000000000000000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0% 0 0% 0 0 0, 0 000000000000000000 0 00 0000000000 .00000000 0000 0n0w0u0n000w0u0n0n0r0n0w0u0x0u0fl0 0 0 0 0 000000000000000000 0 0 0000000000000000000 00 0 000 0 0 0 0 0 0u0u0n0w0n0 0 0 0w 0 u 0 0 0 HG. ll

FIG. 9

EDWIN A. LINK ATTORNEY.

Dec. 5, 1944. v LlNK 2,364,539

CELESTIAL NAVIGATION TRAINER Filed Dec. 28, 1942 ll Sheets-Sheet l0 308 FIG. 10 EDW'N fivwr R.

BYW/Wwz ATTORNEY.

Dec. 5, 1944. L|NK 2,364,539

' GELESTIAL NAVIGATION TRAINER Filed Dec. 28, 1942 ll Sheets-Sheet ll EDWIN A. \LINK INVENTOR.

ATTORNEY.

Patented Dec. 5, 1944 CELESTIAL NAVIGATION TRAINER Edwin A. Link, Binghamton, N. Y.

Application December 28, 1942, Serial No. 470,344

53 Claims.

My invention relates to training devices and is a continuation in part of my co-pending application Serial No. 250,958 filed January 14, 1939.

It is a general object of my present invention to provide in combination with a grounded aviation trainer means whereby a student navigator in a grounded aviation trainer or equivalent device may-take sextant observations upon the stars of a simulated celestial sphere in order that he may determine an assumed position upon the earths surface.

It is a more specific object of my invention to provide in combination with a grounded aviation trainer or equivalent device a simulated celestial sphere which may be made to rotate about said trainer or equivalent device simulation of the apparent rotation of the celestial sphere about the earth caused by a rotation of the earth upon its axis.

It is another object of this invention to provide in combination with a grounded aviation trainer or equivalent device a simulated celestial sphere which may be made to rotate about said trainer or equivalent device in simulation of the apparent rotation of the celestial sphere about the earth caused by a change in the longitue dinal position of the observer.

It is a further object of this invention to pro--' vide in combination with a grounded aviation trainer or equivalent device a simulated celestial sphere which may be f 'llde to rotate about said trainer or equivalent device in simulation of the apparent rotation of the celestial sphere about the earth, which rotation is the result of the apparent trainer or equivalent device in simulation of the apparent rotation of the celestial sphere about the earth caused by a change in the latitudinal position of the observer.

It is another object of my invention to provide means whereby a simulated celestial sphere may be made to change its position relative to a grounded aviation trainer 7 equivalent device according to the passage of time, a change in the longitudinal position of the observer as well as a change inthe latitudinal position of the observer.

Numerous other objects and advantages of my invention'will become apparent as the description proceeds, reference now being made to the accompanying drawings in which like reference numerals indicate like parts. In the drawings,

Fig. 1 is a general side view showing the base, turning means, tower, trainer, simulated celestial sphere, operators desk, means for changing the position of the celestial sphere relative to the trainer, as well as the building in which the apparatus is housed.

Figs. 2 and 3 are detailed views of the dome rail, dome gear box and related parts.

Fig. 4 is a partial cross sectional view of the dome gear box.

Fig. 5 is an exploded view of the systems for driving the simulated celestial sphere and means,

for actuating the indicators.

Fig. 6 is a view of the control panel.

Fig. 7 is a diagranunatic view of the electrical system for controlling the longitude drive and time drive motors.

Fig. 8 is a diagrammatical view of the electrical system for controlling the latitude drive motor.

Fig. 9 is a detailed view of certain parts of the trainer and simulated celestial sphere.

Fig. 10 is a diagrammatic view of the electrical a pulley wheel 24 around which is placed an endless belt 26, which endless belt is also placed around a wheel 28 mounted upon the output sha'it- (not shown) of a turning motor 30. Positioned above the central portion of the angular base 20 is a central hub 32 and fixedly mounted upon the upper end of this hub is a platform 34. Hub 32 contains a suitable beariw airrangement in its lower part just above pinley wheel 24 so that the upper portion of the central hub 32 and platform 34 may rotate while its lower portion and the wheel 24 remain fixed as does triangular support 20. Because turning motor 30 is rigidly aflixed to platform 34, it will be understood that whenever the output driving wheel of this turning motor is made to rotate the arrangement of endlessb'elt 26 and wheel 24 will cause platform 34 to rotate about its vertical axis. The direction of rotation of platform 34 will, of course, depend upon the direction of tuming of the output wheel 28 of turning motor 30. Rigidly mounted upon platfom 34 is a tower assembly 36, and, as seen-in Fig. 9, at the upper end of which is a universal Joint i upon which is mounted the trainer fuselage 38. It will be readily understood, therefore, that whenever,

, through the action of turning motor 30 the platform '34 is made to rotate, the trainer fuselage 38 will likewise respond. Means for causing turning motor 30 to rotate platform 34 and trainer fuselage 38 in response to the aircraft simulating controls within fuselage 38 in exact simulation of the turning of a plane in actual flight in response to movements of the controls within the plane are fully described and disclosed in my issued U. S. Patents 1,825,462 and 2,099,857.

It is to be noticed that supporting tower is not mounted so that its vertical axis coincides with the axis ofrotation 39 of central hub 32, but rather the tower is eccentrically mounted relative thereto. However, trainer fuselage 38 is mounted upon tower 36 in such a manner that the navigators post 4| is directly above the axis "of rotation 39 of central hub 32, and therefore,

whenever the trainer fuselage is turned it rotates about'the navigators post 4|. The axis of rotation of central hub 32 therefore coincides with the axis of rotation of fuselage 38, and, furthermore, these axes if extended would intersect the dome rail at its highest point, or zenith, 43. A weight 53 balances the platform and trainer mounted thereupon.

It will be seen in Figs. 1 and 9 that there are two collapsible-expansible bellows 40 and 42, the former of which is under the right side of the trainer fuselage 38 while the latter is located under the left side of the fuselage. The upper side of bellows 42 is attached to the left underside of fuselage 38 by means of link 45 and the upper side of bellows 40 is similarly connected to the under right side of the fuselage. Attached to the bottom of bellows 40 is a cable 44, the other end 4 collapsed and bellows 40 be expanded the fuselage will bank toward the left. A detailed disclosure of means for collapsing one of these bellows and simultaneously expanding the other in response to the movement of controls within the trainer fuselage 38 so that the fuselage 38 may be made to bank as a result of the movement of controls therein in exact simulation of the banking of a plane in actual-flight in response to the movement of its controls may be found in the above-mentioned U. S. Patents1,825,462 and 2,099,857.

In Figs. 1 and 9 there are also shownv two other bellows 48 and 50. The upper portion of bellows 48 is suitably attached by means of link 41 to a portion of the tower 36 and attached to the lower end of this bellows is cable 49 which runs through a pulley 62 mounted upon the tower 36 as shown. The upper end of this cable is attached to the lower. side of fuselage 38 immediately ahead of the previously mentioned universal joint 5!. A rigid connecting rod 64 has its upper end attached to the lower side of fuselage 38 and its lower end attached to the upper side of bellows 50, and

another rod 66 has its upper end attached to the lower side of bellows 50 and its lower end attached to a short extension 51 mounted upon'the tower assembly 36. Inasmuch as the universal joint 6| lies between the points at which the upper end of cable 49 and connecting rod 54 are attached to the lower side of fuselage 38,,it will be understood that whenever bellows 48 is collapsed and bellows 50 expanded, the trainer fuselage will assume a position in simulation of the diving of a plane in actual flight. On the other hand, if bellows 50 be contracted and bellows 48 expanded, fuselage 38- will assure a climbing attitude. United States Patents 1,825,462 and 2,099,857 also disclose in detail means for causing the trainer 84 and running east-west is a cross piece 66 which.

has integrally formed therewith depending lug 68 which holds the south end of the dome rail 10.

The north end of the dome rail I0 is supported by a dome bracket 12 which is suitably held by some of the cross pieces 62 of the steel framework. Dome gear box 14 is, suspended from the dome rail 10 by means of depending lugs to be later described.

Reference is now made to Figs. 2 and 3 which show in detail the method of suspension of the dome gear box 14 from the dome rail 10. It will be seen in Fig. 2 which shows the side of the dome gear box 14 seen in Fig. 1 that four depending lugs I8, 80, 82, and 84 are attached by suitable bolts 38 to the domegear box. Fig. 3 shows the other side of dome gear box 14. Rollers 88 roll along suitable trackways 90 on the upper side of the dome rail 10 and therefore, the dome gear box 14 may assume any position along dome rail 10. Rollers 92 have suitable trackways 93 along I the sides of the dome rail 10 and therefore make easier the desired movement of the dome gear box along the dome rail. It will be seen that my simulated celestial sphere is attached to dome gear-box 14 so that the simulated celestial sphere moves along dome rail 10 with the dome gear box 14. Although member 95 as disclosed simulates only a portion of the celestial sphere it should be understood that my invention is not restricted to a device simulating approximately the same proportion as shown in Fig. 1, but selectively may include devices which simulate a much larger or smaller part of the celestial sphere. The entire invention is in a suitable building 15.

Reference is now made to Fig. 5 which shows much of the detailed mechanism of this invention. It will be seen in that figure that there is provided a time drive motor 94 which is of the constant speed synchronous type. In the top of this motor there is a suitable reduction searing system 96 so that the output shaft 08 turn at the speed of-two,revolutions' per minute, and

therefore, the gear I which is rigidly mounted upon the end thereof will rotate at the same rate. This gear preferably hasnl teeth and is in mesh with a second gear I02 which preferably has 49 teeth. Gear I02 is rigidly affixed to shaft I04 which ha rigidly mounted upon its other end a third gear I06 having 79 teeth, and gear I06 in turn is in mesh with a fourth gear I08 which has 82 teeth. This last mentioned gear is rigidly mounted upon the end of shaft IIO which has H2 and which shaft has rigidly ailixed to its other end a gear H4. The worm H2 is in working relation with worm gear H6 which isrigidly aflixed to a shaft 8 which is the primary drive of the differential I20. The output shaft I22 of the differential I makes one rotation for each rotation of the input shaft H8, except when the secondary drive I44 of the differential works. Output shaft I22 has rigidly afilxed to its end worm I24 which in turn is in engagement with worm gear I26 which is known as the main drive gear.

A second motor I28 which is known as the longitude drive motor is a series motor reversible and of the variable speed type. This motor has at its 'upper end suitable reduction gearing I30 and the output shaft I32 thereof has integrally formed therewith a worm I34 while at the end of the output shaft in a pinion I36 which is in mesh with a gear I38 which is rigidly mounted upon the central shaft I40 of the lon itudinal transmitter teletorque designated generally as I42. It will be later shown that connected to transmitter teletorque I42 is a receiver teletorque and connected to each of the other transmitter teletorques hereinafter described in a corresponding receiver teletorque. The transmitter and receiver teletorques of each system are connected in a mannerwell understood in the art so that the output shaft of the receiver teletorque rotates in the desired direction through the same angle as the input shaft of the transmitter teletorque.

The worm I34 which is integral with the output shaft I32 works in relation to worm gear I44 which is rigidly aflixed to the yoke of differential I20. The output shaft I22 of diflerential I20 is movable inside gear I44. It will therefore be realized that worm gear I44 is a secondary drive to differential I20 and that the shaft I22 gives an output which is the resultant of the driving of-time drive motor 94 and the longitude drive motor I28.

In order that the utility of the above-described system will. be appreciated, reference must be made to the fundamental principles of celestial navigation. 7

Ordinary civil time is ,based on the rotation of the earth with respect to the sun, the civil day being the average period of time required for one complete revolution. The'sidereal day is defined as the length of time required for the earth to make one complete rotation with respect to the stars. Because the earth is moving in a path around the sun at the same time that it is turning upon its axis,- for 365 civil daysthere are 366 sidereal days, or thecivil day is longer than the sidereal day by an amount equal to about 3 minutes 56 seconds. This being true, it will be realordinary civil time. 1

This being the case, it is evident that the simu. lated celestial sphere which forms an important part of my invention must be made by thetime drive mqotor 04 and intermediate gearing .mechanism to rotate through exactly 360 59' in 24 hours. This difference between the length of a civil day and the length of a sidereal day makes neessary the employment of the gears mentioned above I00, I02, I06 and I08 which gears are referred to as the time transfer mechanism. By providing a ratio between worm I24 and the main drive gear I26 in the first instance, and a ratio between worm I I2 and worm gear H6 in the second instance such that two revolutions per minute of the 'shaft IIII will rotate the main drive gear I26 through exactly 360 in 24 hours, it is evident that if gear I08 and shaft IIO are driven at the correct rate slightly in excess oi two revolutions per minute, the main drive gear I26and simulated celestial sphere 95 can be made to rotate through exactly 360 59 in 24, hours. By the employment of gears I00, I02, I06 and I08, each of which has the number of teeth mentioned above, the output of time drive motor 94 as represented by the number of revolutions per minute made by its output shaft 98 is increased so that the speed of shaft H0 is to the speed of shaft 98 as 360 59' is to 360 and, therefore, the main drive gear I26, in the absence of any movement of the secondary driv I44 of diiferential I20 and simulated celestial sphere 05 will be made to rotate through 360 59' in exactly 24 hours.

This being the case, it will be readily understood that upon energization of time drive motor 94 a movement will be imparted to my simulated celestial sphere 95 exactly equal to the apparent movement of the real celestial sphere about any given point on the earths surface caused by the rotation of the earth upon its axis.

It will be readily understood that if an observer upon the surface of the earth be traveling westward, that is, in the same directionas the apparent traveling of the stars, the apparent motion of the stars will be decreased while if an observer be traveling eastward the apparent movement of the celestial bodies will be increased. Therefore, I have provided the longitude drive motor I28 to drive the worm I34 which in turn drives worm gear I44 and the yoke of differential I20. It will be readily realized that inasmuch as longitude drive motor I28 is of the series reversible variable speed type,the output of differential I20 due to the running of time drive motor 'decreased according to the assumed direction of travel of an observer as well as according to the assumed speed of his travel. The electricalclrwit and various controls of time drive motor 04 and longitude drive motor I28 will be discussed hereinafter.

Reference is now made to Fig. 4 which is a detailed cross sectional view of a portion of the dome gear box I4. There is provided a central shaft I45 the upper end of which has rigidly .afllxed thereon a cone I40 and upon which in turn is mounted tapered roller bearing cage I40 ing cage I62 and inside this cage is placed lower bearing cone I64. A shoulder I66 of central shaft I45 rests upon cone I64. It will therefore be realized that central shaft I45 is held within the dome gear box by the upward action of members I6I, I62, and I64 and by the downward action of members I46, I48, and I50. The outside I54 of the dome gear box is suspended from the dome rail by means of the previously-described depending lugs 18, 80, 82 and 84.

It should be borne in mind thatthe presence of bearing cages I48 and I62 make it possible for central shaft I45 to rotate within the dome gear box.

It will be seen from 'Fig. 4 that the main drive gear I26 to which reference has been made in my discussion of Fig. is within the dome geari box and that worm I24 which drives the same is also therein. Whenever worm main drive gear I26 central shaft I45 is made to rotate.

As seen in Fig. 4, worm I24 drives main'drive gear I 26 which in turn drives shaft I45 whenever the clutch designated generally by I21 is engaged. This clutch forms no part of the instant invention but for a full disclosure, thereof reference is made to the copending application Serial Number 480,330, filed March 24, 1943. In Fig. 2 the clutch reset mechanism is designated generally by I29, and for a full disclosure thereof reference is made to the same copending application.

Central shaft I45 projects below the lower housing I58 of the dome gear box, and as best seen in Figs. 2 and 3, a collector ring assembly I68 is mounted on central shaft I45 below housing I58 and -by means of a suitable set screw (not shown) is rigidly aflixed thereto. Central shaft I45 immediately below collector ring assembly I68 begins to taper and the inside of the dome hlub I10 is also tapered so that the dome hub I10 when pushed up on to central shaft I45 stops at the correct point. Nut I12 is then screwed onto the threaded lower end of shaft I45 and holds the inside tapered surface of hub I10 fast against the tapered lower portion of shaft I45. Therefore, whenever central shaft I45 is rotated dome hub I10 and the simulated celestial sphere 95 rotate tioned at a fixed point upon the earths surface.

and such fixed rotation may be modified to simulate the rotation of the real celestial sphere about an observer traveling at any speed, east or west, at any rate upon the earth's surface.

Reference is now made to Fig. 6 which shows the operator's control panel. It will be seen that on that panel is a simple off-on switch I14 designated by the word Time.

This switch controls time drive motor 94 and I24 drives the whenever it is in the on position, provided certain other switches be correctly positioned, as will hereinafter be described, time motor 84 drives, through the previously disclosed intermediate mechanism, main drive gear I26, and consequently, the simulated celestial sphere 95 rotates through exactly 360 59 in 24 hours. Simulated celestial sphere 95 will therefore rotate about the trainer at the same rate that the real celestial sphere apparently rotates about any given point on the earths surface because of the turning of the earth upon its axis.

In Fig. 6 it will be seen that there is also pro- .vided longitude switch I16 having a neutral, W

(west) and E (east) position as well as a 1ongitude variac I18 and a longitude speed control I80. Also provided is a master switch I82 and a navigation switch I84. I

Reference is now made to Fig. 7 which shows in detail the electrical control system of the longitude drive motor- I 28. It will be seen that whenever the master switch I82 is in the on position and the navigation switch I84 is likewise positioned, current will flow through the longitude variac I18, and provided this variac be turned up, to the longitude direction switch I16. The term variac when used herein designates an auto-transformer with a continuously variable tap. The direction of flow through the armature I86 will depend upon whether the longitude direction switch I16 be on the side designated E or on the side designated W. Therefore, the direction of turning of longitude drive motor I28 will be determined by the position of switch I16, and the output of differential I20,seen in Fig. 5, will be increased or decreased by the position of longitude direction switch I16. Specifically, if an observer on the earth's surface were traveling in an easterly direction, the real celestial sphere would apparently rotate toward the west at a greater rate than if the observer were not traveling. Therefore, if it be assumed that the trainer beflying in an easterly direction, the simulated celestial sphere must be rotated at a greater rate of speed. This is accomplished by throwing the longitude direction switch I16 to the E position. 1

Longitude drive motor I28 will therefore turn in such a direction that the output of differential I20 is increased and main drive gear I26 and the simulated celestial sphere will rotate at an increased rate.

On the other hand, if an observer were actually traveling in a westerly direction, the apparent rotation of the real celestial sphere would be decreased according to the speed of his travel. In order that this may be simulated with my invention, whenever it is assumed that the trainer is traveling toward the west the longitude direction switch I16 is placed in the W position and as a result the longitude drive motor I28 will turn in such a direction as to decrease the output oft-differential I20 and, therefore, main drive gear' I26 and the simulated celestial sphere will turn at a rate slower than when time drive mo tor 94 is the only one running.

Referring to Fig. '7, it will be readily understood that by varying the position of longitude variac control I18 upon the control panel shown in Fig. 6, the speed of longitude drive motor I28 may be controlled.

A second means of controlling the speed of longitude drive motor I28 is also shown in Fig. 7. This control takes the form of a plurality of interrupter cams I88, I90, I92 and I94 which are rotated by any constant speed motor (not shown) controlling the positions of selectorarms 204 and 206. It will be seen that whenever master switch I82 and navigation switch I84 are closed, current will flow through the wire 208 and through selector arm 204. If longitude speed control I80 be in the 1 position, current will flow through wire 2 I and whenever contact point I96 is closed by cam I88 through wire 2 I2 and if contact point 202 is closed by cam I94 and contact point 200 is closed by cam I92 andcontact point I98 is closed by cam I90, current will flow along conductor 2I4 through selector arm 206 and through longitude relay 2I6, then through wire 248 out through the master switch I82. It will therefore be realized that for longitude relay 2 I6 to be energized when longitude speed control I16 is in the "1 position, all four of the cams I88, I90, I92 and I94 must be so positioned that the circuit is closed and, longitude drive motor I28 can run only when the longitude relay 2I6 is energized and the circuit is closed at the points 220.

Whenever longitude speed control I80 is placed in the 2 position, longitude relay 2I6 is energized only when cams- I88, I94, and I92 simultaneously close the circuit, and therefore motor I28 can run only when these three cams are simultaneously so positioned.

Study of the cam control electrical circuits of .Fig. 7 will show that the longitude motor may be made to run varying proportions of the time by changing the position of longitude speed control I80. Furthermore, the speed of the longi tude drive motor I28 may be controlled by the position of longitude variac I18. These two variables make it possible to control the rotation of the output shaft I32 of the longitude drive motor I28 and therefore to modify the rate of rotation of the simulated celestial sphere as turned by the time drive motor 94. As stated previously, the speed and direction of the turning of the output shaft I32 of the longitude drive motor I28 will depend upon the assumed direction of travel of the trainer as well as the assumed speed 'thereof.the assumed rate of change of longi tude of the trainer.

Fromthe foregoing description it will be seen that by throwing the time switch I14 to the on position, the simulated celestial sphere will be made to rotate about the trainer at the same rate that the real celestial sphere rotates about a given point on the earths surface. If the trainer is assumed to be going eastward or westward, by means of longitude direction switch I16, variac H8 and longitude .speed control I80, the speed of rotation of the simulated celestial sphere may be increased or decreased by exactlythe right amount so'th'atthe fate of turning of the real celestial sphere caused by one traveling in that direction and at that rate upon the earths surface may be exactly simulated.

Means for rotating simulated celestial sphere in simulation of apparent rotation of real celestial sphere about the earth due to a change in 0bser'oers latitudinal position understood that if an observer is traveling from the weight 244.

north or south, 1. e., if his latitudinal position be changing, the real celestial sphere will make an apparent rotation at right angles to the rotation caused by the rotation of the earth and the change in the longitudinal position of the observer. The following means have been incorporated in this invention in order that the apparent rotation of the real celestial sphere caused by a change in the latitudinal position of the observer may be simulated.

It can be seen in Fig. 1 that the dome rail has suspended thereupon the dome gear box 14 which in turn holds the simulated celestial sphere. It will be seen that as the dome gear box 14 is moved from the uppermost portion of the dome rail 10 toward the lower end the angular relationship of the simulated celestial sphere 95 to the trainer 38 and to the navigators post H is changed.

The real north celestial pole is exactly above the real north terrestrial pole and in my invention the simulated north celestial pole is on the axis of the central shaft I45 of the dome gear box. When the simulated celestial sphere is exactly above the navigators post H in the trainer 38 the simulated stars inside the simulated celestial sphere 95 bear the same relationship to the navigators post M as the stars of the real celestial sphere bear to an observer positioned at the north terrestrial pole. At the north terrestrial pole the north celestial pole is in the zenith of the observer, that is, is directly overhead or has an elevation of 90. If the observer were to travel toward the south terrestrial pole it will be realized that the north celestial pole will no longer be in the zenith of the observer but rather it will move toward his horizon, or expressing it in another manner, its altitude will decrease. It can be seen that by a movement of the dome gear box 14 down the dome rail 10 the simulated north celestial pole may be made to approach the horizon of the observer'in the trainer and the altitude of this pole will decrease. Therefore, it is possible by moving the dome gear box 14 along dome rail 10 to simulate the rotation of the real celestial sphere caused by a change in the latitudinal position of the observer upon the surface of the earth.

As previously explained in our discussion of Figs. 2 and 3, the dome gear box 14, is suspended irom the dome rail 10 by means of four lugs 18, 80, 82 and 84 and a plurality of rollers 88 and 92 facilitate movement of the gear box along the rail. Referring to Figs. 1, 2 and 3, it will be seen that attached to the lugs 18 and is a cable :222 which travels in pulleys 224 which are mounted on the upper surface of dome rail 10. Cable 222 extends toward the south of the building, as seen in Fig. 1, and is in engagement with pulleys 226 and 228 which are suitably mounted upon the steel framework. Cable 222 then descends and travels along a suitable retaining track 230 on the arcuate outer portion of the dome counterweight sector 232. The cable is aillxed to the dome counterweight sector near A second cable 284 is attached to the other two depending lugs 82 and 84' which hold the dome gear box 14 and likewise travels along a plurality of pulleys 236 also suitably mounted onthe upper surface of dome rail 10. This cable terminates at the latitude drive motor 230.

It will be noticed that the dome counterweight sector 232 is pivoted for movement about the counterweight sector is suspended in such a direction that a minimum of weight tends to prevent the dome gear box anad celestial sphere from traveling down the dome rail, but as the dome gear box 14 and celestial sphere 96 move down the dome rail 16 it will be readily understood that inasmuch as the direction of movement becomes increasingly perpendicular a greater force will have to be exerted upon the cable 222 in order to prevent the dome gear box 14 and simulated celestial sphere from traveling further down dome rail 16. Therefore, it will be seen that as the dome gear box 14 and simulated celestial sphere move down dome rail 16 weight 244 is moved from its vertical depending position to a more horizontal extended position, and therefore,

a greater pull will be exerted upon cable 222 thereby preventing the dome gear box 14 and simulated celestial sphere from moving farther down dome rail 16. No matter what position dome gear box 14 and simulated celestial sphere 65 occupy along the dome rail16, the dome counterweight sector always exerts sufllcient pull on cable 222 to pull the gear box and attached sphere up the rail, in the absence of any other force tending to pull them down the rail.

In the event it is desired. to move dome gear box 14 and simulated celestial sphere 66 down dome rail 16 sufllcient pull is applied to cable 234 by means of the latitude drive motor 238 to overcome the tendency of dome gear box 16 and simulated celestial sphere to move up dome rail 16 as a result of the pull exerted upon cable 222 by dome counterweight sector 662.

Reference is now made to Figs. 6 and 8 which disclose the means for controlling the position of gear box 14 and simulated celestial sphere 65 on dome rail 16 in order that the simulated celes- 4 tial sphere may change i% (position relative to the observer's post within the trainer fuselage 66 in the same manner that the real celestial sphere changes its position relative to an observer whose latitudinal location upon the surface of the earth is changed.

It will beseen in Fig. 6 that there is pro vided a latitude switch 246 having a neutral, N (north) and S (south) positions. Assuming that the master switch I 82 and the navigation switch I64 be closed, current will flow in through the switches and along conductor the latitude variac 256 and, if this variac be turned up, along wire 252. Assumingthat latitude switch 246 be in the S position, current will flow along conductor 254 toward the bottom of Fig. 8 to the left through the coil 266 of latitude drive motor 238 and up conductor 262, along conductor 264 through latitude di- 248 through rection control switch 246 along conductor 266,

down this same conductor through the latitude relay 268, if that relay be closed, through the armature 216 of latitude drive motor 238 and, by means of conductor 212, out to main line 214 and out through the navigation switch I84 and master switch I82. In the event that latitude control switch 246 be in the N position current will flow in through conductor 248 through variac 256 along conductor 252 and then at the latitude direction control switch 246 will be led along conductor 216, down conductor 262 and to the right through coil 266- of latitude drive motor 236, up conductor 254, along conductor 218 toward the left in Fig. 8 and through latitude direction control switch 246 along conductor 266, down conductor 266 to latitude relay 268, and if this relay be closed, to the right through the armature 216 of latitude drive motor 238, down and along conductor 212 to main line 214 and out through navigation switch I64 and master switch I82.

. It is to be noted that when latitude direction control switch 246 is in the S position, current flows through the coil 266 of latitude drive motor 238 toward .the left of Fig. 8, but when latitude direction control switch 246 be in the N position current through coil 266 is toward the right in Fig. 8. In both instances, current flows through armature 216 toward the right in Fig. 8. This reversing of current through coil 266, it will be understood, will reverse the direction of the output of latitude drive motor 238 and therefore, the dome gear box 14 and simulated celestial sphere can be made to move in either direction along dome rail 16. Specifically, if latitude directioncontrol switch 246 be in the S position, latitude drive motor 238 pulls, by means of cable 264, the dome gear box 14 and simulated celestial sphere down dome rail 16, but in the event latitude direction control switch 246 be in the N position, latitude drive motor 236 has an output in a direction to release cable 234 and dome counterweight sector 262 will then pull dome gear box 14 and simulated celestial sphere up dome rail 16.

It is to be noted that whenever master switch I82 and navigation switch I64 be closed, cam drive motor 219 which is of the constant speed type will rotate interrupter cams 266 at a constant rate. These cams perform the same function that cams I88, I66, I62 and I64 perform in the longitude motor circuit. Latitude speed control 262, as seen in Fig. 6, is in reality a gang switch as seen in Fig. 8 having two contact arms 28d and 286. By positioning latitude speed switch 282 the proportion of time which the latitude relay 288 will be energized and the circuit closedat the points 266 will be varied, and

. therefore, latitude drive motor 238 may be made Means for simulating stars a The simulated celestial sphere 65 which forms an important part of this invention is generally spherical in shape and has, as shown in Fig. 9,

a frame comprising aluminum ribs 266 which preserve the desired shape of the sphere. Suitably attached to the inner set of these ribs is a wire mesh 262, and light sockets 264 representative of stars are mounted in some of the holes in the screen 262. These sockets are positioned upon the simulated celestial sphere so that they bear the same relative relation to one another and to the north celestial pole of the simulated celestial sphere as do the real stars which they represent bear to one another and to the real conductors 298 and around each of these bulbs is placed a cylinder (not shown) whose axis points toward the navigators post M in the trainer, and over the end of the cylinder is placed suitable covering material having a very small aperture therein. By this arrangement, the navigator sees a relatively smallsource of light which to him looks like a star.

Naci gational stars In celestial navigation, although countless stars may be seen by the navigator, observations by the use of the sextant are made upon very few of them. Those stars upon which observations are made are all well-known and are fairly evenly distributed on the celestial sphere and are commonly referred to as the navigational stars. Those skilled in the art of celestial navigation will realize that the fundamental use of the sextant is to determine the altitude of the star under observation above the horizontal plane of the observing navigator. In practical navigation, the observed altitude must be accurate within a few minutes of arc in order that thernavigator will be able to determine his position upon the earth .within satisfactory navigational limits.

It will be readily understood that inasmuch as the diameter of the simulated celestial sphere must be limited to a few yards. a movement of the sextant of a relatively small distance within the simulated celestialisphere will make a relatively large difference in the observed altitude of any star upon the inside of the simulated celestial sphere, or expressing it in another manner a movement of one inch of the sextant within the simulated celestial sphere would change'the observed altitude of the stars as much as a movement of several mile upon the earth's surface would change the observed altitude of the real stars. Therefore, there is incorporated in my invention the use of a plurality of collimators 300 such as are disclosed in United States Patent 2,310,031 dated Feb. 2, 1943, one of which is associated with each of the navigational stars within the simulated celestial sphere. Such an instrument has within its casing means for producing an apparent point source of light and employs a collimating objective lens which renders all rays passing therethrough parallel. There is,

therefore, a projection of parallel rays emanat ing from the collimator having a. cross sectional area equal to that of the oollimating lens. When the observer's eye is within any part of the path of these parallel rays. he sees the apparent point allel rays, he does not see the source of light. Each of the collimators 300 is exactly positioned within the simulated celestial sphere so that the parallel rays emanating therefrom intercept at the navigators post II in the trainer fuselage 38. The navigator in the fuselage 38, by placing his sextant within the area of parallel rays-coming from any one of the collimated navigational stars can determine the altitude of the star above the horizontal within practical navigational limits because all of the parallel rays emanating from the apparent point source of light within the collimator make the'same angle with any horizontal plane in which the sextant may be placed for an observation. If the sextant is placed outside the parallel rays, no observation may be taken. Therefore, for a given position of simulated celestial sphere only one observed altitude of any given navigational star may be obtained. It is the function of the operator to position the simulated celestial sphere relative to the navigator's post 4| so that the navigator gets an observation equivalent to that which he would get if his actual position upon the earth's surface corresponded to that of the assumed position of the trainer.

It should be stated that the collimators "I must be accurately positioned about the simulated celestial sphere so that they occupy the same position relative to one another that the stars which they represent occupy relative to one another in the real celestial sphere- With the dome 95 at the zenith of the rail 10, the collimators may be originally adjusted by any suitable means to the correct declination and LHAY. The non-navigational or uncollimated stars need not be so adjusted.

It will be readily understood that in the event that the atmosphere is hazy the lesser bright stars are the first to become invisible and, as the atmosphere gets heavier, more and more stars disappear from sight. When it is clear the stars appear much brighter than when atmospheric conditions are otherwise.' In celestial navigation the stars are grouped into one of three classes: navigational, constellational, and miscellaneous.

As above explained, the navigational stars are those-upon which the navigator takes observations with the aid of his sextant; such as Polaris. The constellatlonal stars are those which are used by the navigator in order to locate the navigational stars, for example, it is well known that the two end stars of the Big Dipper, which is a constellation, point toward Polaris which is a navigational star. Some of the navigational stars Means for lighting miscellaneous stars.

Reference is made to Figs. 6 and 10 which show the means for lighting, the desired simulated stars upon the inside or the celestial dome. It

will be seen in Figs. 6 and 10 that whenever master switch I82 is in the "on" position and the stars switch 302 is,also in the on" position a voltage (ordinarily is impressed across the terminals of the star density control variac I.

.If the variable contact arm 308 of variac 304 be moved clockwiseto some position along variac 304 a voltage will be, impressedon conductor "8' and along conductor 3". 'If the miscellaneous stars switch 3P2 be closed current will be led along conductor an to brush M6 and to slip-ring 3|8 from whence it is carried to the transformers 320. which are arranged in parallel. Current flows through the primaries MI and then by means of line!" passesthroughslip-ring 324,

brush 326', conductors 328. and 330, through master switch I82 back to the generator. The flow of current through the primary windings "I ofthe transformers 320'induces a voltage in the secondary windings 332 which causes a current to flow through conductor 334 and :bus bar 325 to the miscellaneous stars 336. All the bus bars are designated in Figs. 2, 3, and by 325.

' From these stars the current passes through the ground 292, which it will be recalled is the wire mesh, and then passes back to the other side of desired by positioning star density control variac Means for lighting navigational (collimated) starsv A study of Fig. 10 further reveals that by closing master switch I82, stars switch 302,'and by correctly positioning variac ass, current will flow along conductor 33$ and if constellation switch 360, which is also shown in Fig. 6, be in the on position, current will pass along conductor 342,

'If collimator recognition relay 3st is not energized, as is the case in Fig. 10, current will pass through the relay and. along conductor 348 to brush 35-5, slip-ring 359 and through the primary winding 35: of the transformer 353. From there energized. These lights, about to be disclosed in detail, are visible from any point within the simulated celestial sphere 95.

Reference is made to Fig. 11 which discloses'a collimator 388 having a collimating objective lens flector 314 having a convex side toward recognition star lamp 316. Within this lamp, which is identical with the star lamps 294 mounted in the Sil current flows along conductor d and through the common return circuit which comprises slip ring 32-5, brush 328 and conductor 323. A voltage will therefore be induced in the secondary winding 356 of the transformer and the apparent point sources of light 335 in the collimators act will be energized. It will be recalled-that these lights in the collimators simulate the navigational stars. Current leaves the collimator-shy means of the common ground 292 which, as stated above, is the wire mesh, and is returned by means of conductor 339 to the other side of the transformer.

It will be seen from Fig. it that if the collimator recognition switch 355 be closed collimator recognition relay 344 will be energized and there fore current flowing from the constellation switch 340 through conductor 34?. will not pass along conductor 346 to the collimators but instead will pass along conductor 360 to brush 362, slip-ring 364 and to the primary winding 36%; of the trans" former 361. A current will be induced in the secondary 388 of the transformer and, the lights 3'") which are known as the recognition lights will be energized. The switch 358 is located on the navigators panel inside the trainer fuselage 38 and, therefore, the navigator has within his control whether the collimated stars 335 or the recognition stars in the interior of the celestial sphere shall be seen by him. Such means are important because, as previously explained, the

rays emanating from the point source of light 335 within the collimators 300 are visible to the navigator only when his eye is in the path of the relatively small projection of rays coming from the collimators 300. In order that the navigator may easily locate the collimated navigational stars the switch 358 is provided. vWhen this switch is in the off position collimator recognition relay 344 is not energized and the collimated stars 335 may be seen. However, when switch 358 is closed collimator recognition relay Us energized and the recognition lights 310 are wire mesh 292 is a bulb (not shown) energized by means of conductor 318. Light emanates from socket 316 through aperture 380 and is reflected by glass reflector 314 toward the observers post in the trainer fuselage 38. The reflected rays will be visible from any point near the navigators post, and, therefore, will enable him to locate the approximate position of the navigational stars. Having done this, by throwing switch 358 from the closed to the open position collimator recognition relay 344 loses its energization and, as previously explained, the collimated navigational stars 335 will'become energized, while the recognition stars 318 will be shut off.

Means for lighting constellations I be closed current will be carried along conductor '382 to switch 384 which is also seen in Fig. 6.

If this last-mentioned switch be closed, current will he carried by conductor 386 to brush 383 and siip-ring 393 to the primary windings 392 of the transformers 391i, and from these primaries to the common return 322. A voltage will therefore be induced'in the secondary windings 395 which will cause the constellation lights 463 to he energized. The return circuit to the secondaries 386 is, as in the previously-explained instances, through the common ground 292.

The constellation lights 4% are energized whenever switch 384 is closed provided switch 340 also is closed because switch 340 is in series with switch 384. Switch 340 also controls the flow of current through conductor 342 and the collimator recognition relay, and, therefore, it will be realized that whenever the constellation lights 603 are energized by closing of switches 384 and 343, either the collimated lights 335 or the recognition lights 310 are also energized, depending upon the position of the collimator recognition switch 358- upon the navigators panel in the trainer fuselage 3%.

From the foregoing description it will be realized that the operator, .by means of the miscellaneous stars switch 3|2 may illuminate the miscellaneous stars of the simulated celestial sphere as desired; and by means of switch 348 the operator may make it possible forthev navigator to illuminate either the collimated navigational stars or the recognition'stars; and the navigator may, by means of switches 334 and 340, illuminate the constellation stars.

Indicators time, a change in the longitudinal position of the observer as well as a change in the latitn change its position rela- 7 two to the fuselage according to the passage of position of the observer, it will be realized that the operator must have within his sight instruments which will tell him at all times the assumed time, the position oi! the simulated celestial sphere as well as the assumed position of the trainer upon the earths surface.

An important concept in the field of celestial navigation is the Local Hour Angle of Aries, abbreviated LHAY. Aries is a point upon the celestial sphere, and inasmuch as the celestial sphere may be considered stationary, Aries is a fixed point. Inasmuch as the earth rotates upon its axis it will be realized that the point on the earth directly adjacent Aries is constantly changing. The difference in longitude between any point upon the earths surface and the longitude of the point upon the earth directly beneath Aries is known as the Local Hour Angle of Aries.

Inasmuch as the earth is constantly rotating on its axis within the celestial sphere it will be realized that the LHAY of any given point upon the earths surface is constantly varying and inasmuch as the celestial sphere makes an apparent rotation of 360 59 about any given point upon the earth in 24 hours, it will be realized that the LHAY of anygiven point will vary through an equal number of degrees in that length of time or that it will vary through 360 in slightly less than '24 hours. Thus, if an observer be stationed at a' given point upon the earths surface his LHAY will vary with the rotation of the earth but if the observer be traveling upon the surface of the earth the change in hlS LHAY will be the result Of that which is caused by the rotation of the earth as modified by his movement upon the earth. If the observer be traveling in the'same direction as the rotation of the earth his rate of change in LHAY will be accelerated while if he alters his longitudinal position in a direction opposite that of the rotation of the earth his rate of change in LHAY will be decreased. It is therefore evident that the LHAY of an observer depends upon two factors: time and longitudinal position upon the surface of the earth.

It is apparent that if the operator is to maintain the simulated celestial sphere in a position gear 402 rotate through a given number of degrees the hands and dial of indicator 422 indicate the number of degrees of movement, LHAY indicator 422 is shown uponthe instrument panel 405 of the operator's desk 450 in Fig. 12.

Also shown in Fig. 5 is the longitude transmitter I42 to which reference has been previously made. This transmitter is connected to the central shaft of receiver 424 in the same manner that the LHAY transmitter 4 is connected with the central shaft of receiver U0 'and, therefore, the central shaft of receiver 424 is gearedto hands 426 in such a mannerthat these hands move across the dial of indicator 428 to show the number of degrees that the simulated celestial sphere and annular gear 402 rotate as a. result of the running of longitude drive motor I28. Longitude indicator 423 is also shown in Fig. 12.

It will be recalled that time drive motor 94 drives shaft 98 at the rate of two revolutions per minute and that gears I00, I02, I05 and I08 step up the rotation of shaft 90 slightly because of the difference in the length of a sidereal and solar day. Gear II4 will therefore make slightly more than two revolutions per minute and, as seen in Fig. 5, this gear is in working relation with another gear 430 which is rigidly mounted upon the input shaft 432 of time transmitter 434 which is of the same type as transmitters I42 and M4. This transmitter is connected to a receiver 436 in the same manner that transmitters I42 and 4M are connected to their respective re- I02, I06 and I08 it is possible to reduce the effect relative to the navigators post H in the trainer place upon the earth's surface at a given time,

he must know the assumed time as well as the assumed longitudinal and latitudinal position of the trainer.

Reference is made to Fig. 5 which shows the central hub I10 which, it will be recalled, is mounted upon central shaft I45 for rotation therewith. An annular gear 402 is integral with the upper portion of'this central hub and mounted in workable relation to this annular .gear is pinion 404 which is rigidly mounted upon vertical shaft 400, to the. other end of which is rigidly ailixed another gear 400. Pinion 4I0, which in turn is in. workable relation with gear 403, is integral with shaft 4I2which is the input shaft of the LHAY transmitter "4. This transmitter is connected to a receiver 8 of similar type by means-of cable 4|! so that the central shaft (not of the rotation of the central shaft of the receiver 435 to the same speed of rotation as shaft 98. Having thus reduced the speed of rotation of shaft 4 in this manner, clock hands 438 may easilybe made to give the elapse of solar (civil) time. Clock 440 therefore indicates the exact amount of time that time motor'94 runs. This clock is also shown in Fig. 12.

One of these, clocks 440 is provided for the operator, and inasmuch as the element of time must also be' known by the navigator, a similar clock is provided for the navigator in the trainer fuselage 38. Consequen ly, the operator and the navigator both have synchronized time indicators.

Also seen in Fig. 5 is a section of dome rail 10. Along one side of the top of this rail is a series of holes 443. Latitude transmitter 442 which is of the same type as transmitters I42, 4 and 434 has an input shaft 444 upon the end of which is mounted roller 446. This roller has a plurality of upraised portions 448 evenly spaced around the roller and the holes 443 in the dome rail I0 are spaced so that the upraised portions 440 of the roller fall therein as the latitude teletorque transmitter 442 is moved up or down the dome rail'as a result of a movement of the dome gear box I4. It will be seen in Fig. 3 that the latitude teletorque transmitter 442 is mounted upon the dome gear box and therefore the roller 443 and input shaft 444 will rotate as the dome gear box I4 and simulated celestial sphere move along the dome rail. Transmitter 442-is connected by means of cable 450 with a teletorque receiver 452 which has connected to its central shaft hands 454 which move across the dial of indicator 4". The central shaft oi" the receiver 452, hands 434 

